The goal of this research is to study the chemistry of the early events in hormone action. Initial response of cells to some classes of hormones (polypeptides, catecholamines, prostaglandins) can be divided into two parts: the specific binding of the hormone to cell surface receptors and the subsequent activation of plasma membrane-bound adenylate cyclase. I propose to isolate and purify adenylate cyclase from bovine brain and from kidney. Progress has already been made toward characterizing and purifying the detergent-solubilized enzyme from these sources. The next phases of the project will exploit specific properties of the enzyme to achieve complete purification. In order to design new, specific purification techniques, further characterization of the partially purified enzyme is needed. These studies will include investigation of the possible role of a separable enzyme subunit in mediating guanine nucleotide activation, and of the role of metal ions in maintaining the structure and activity of adenylate cyclase. In addition to contributing to the development of purification techniques, studies such as these will yield new information about factors which control adeynlate cyclase activity. Purified adenylate cyclase will be characterized chemically and immunologically. Specific antibodies will be made to the pure enzyme. These will be used to examine the degree of similarity among adenylate cyclase from different cell types. The availability of specific antibodies will make possible the development of a radioimmunoassay for the enzyme. It will then be possible to quantitate adenylate cyclase so that the basis of the abnormal levels of the enzyme as are found in malignant cells and in other disease states may be studied. Eventually receptors for the hormones which activate these adenylate cyclases must be isolated as well so that one can studiy the nature of the interaction between the receptor and the enzyme in a reconstituted system. However, the present studies are a necessary first step toward understanding the chemistry of hormonal control of cell function.